Nguyen Thanh Duy and Duong Nguyen Khang

Abstract

This study focused on the effect of coconut oil meal on growth performance
and methane emissions in growing cattle fed Elephang grass and cassava pulp. Twenty female Sindhi cattle were
allocated to five treatments in five pens according to a randomized complete
block design (RCBD). The treatments were levels of coconut oil meal of: 0,
0.25, 0.5, 0.75 and 1.0 percent of live weight per day. The basal diet was
fresh cassava pulp and elephant grass fed at levels of 1 and 2% of live
weight (DM basis), respectively.

Growth rate was increased, feed conversion was improved and eructed methane
decreased with increasing amounts of coconut oil meal in the diet. The
solubility of the diet protein was reduced when the coconut meal
concentration in the diet increased and was directly related to the
reduction in eructed methane. A direct effect of the oil in the coconut meal reducing
methanogenesis through indirect effects on rumen protozoa population may
also have contributed to the reduction in methane when Elephant grass was
supplemented with coconut meal.

Introduction

Cassava is one of the major crops planted in the tropics. It is cultivated in
Viet Nam mainly for food (sweet varieties) and industrial starch (bitter
varieties), and recently for feeding to livestock. The increasing demand for
cassava for industrial use has resulted in the production of large
quantities of byproducts and residues. Cassava pulp is the major byproduct
accounting for some 30% of the original root. It is composed almost
completely of non-structural carbohydrate, 65% of which is starch according
to Sriroth et al (2000). It is very low in crude protein (less than 3% in
the dry matter) and in minerals. To take advantage of the high carbohydrate
content of cassava pulp it is recommended (Phanthavong et al 2016) that it
should be supplemented with:

Fermentable nitrogen that will produce the ammonia needed to optimize
the growth of the microbes in the rumen

Protein that will by-pass the rumen to complement that produced by the
rumen microbes

A source of fiber that will act as the support structure for the
formation of biofilms (Leng 2014) which is where rumen microbes and
their required nutrients come together to optimize the digestive process
in the rumen

Minerals, especially sulphur but also salts of calcium, phosphorus and
sodium.

The coconut tree is an important source of edible oil in Vietnam; the area
planted is of the order of 163,200 ha, with oil production of around 968
thousand tonnes (Statistical book 2002). Coconut meal is the byproduct from
the extraction of oil, representing from 34 to 42% of the weight of the nut
(Hutagalung 1981). It contains 18 to 25 % crude protein in DM. When the
mechanical expeller process is used to extract the oil, the protein-rich
byproduct is likely to be a good source of “bypass” protein, as the
combination of the heat produced in processing, and the presence of residual
oil, will tend to protect the protein against degradation in the rumen, thus
conferring rumen “bypass” or “escape” properties to the protein (Preston and
Leng 1987).

Elephant grass is considered to be the fastest growing plant in the world
(Karlsson and Vasil 1985). However, when fed as the sole compoonent of the
diet of fattening cattle, growth rates were low (111 to 260 g/day; Antari et al
2016). of weverThe protein content ranges from 4.4 to 20.4% in
dry matter (DM) with the mean around 12%; the average NDF and ADF values are
around 67 and 42%, respectively (Rusdy 2016). It could thus provide the
fermentable protein and the fiber needed to optimize rumen microbial
fermentation of the cassava pulp.

The purpose of the research reported in this paper was to evaluate the
effects on growth rate, and on enteric methane production in Sindhi cattle, when
Elephant grass was supplemented with a combination of cassava pulp and coconut
oil meal.

Materials and methods

Location

The experiment was conducted in the cattle farm of the Research and
Technology Transfer Center of Nong Lam University from February to May 2016.

Treatments and experimental design

Twenty female Sindhi cattle were allocated to five pens according to live
weight and fed a basal diet of Elephant grass and fresh cassava pulp (2 and
1% of live weight, as DM, respectively). Each pen received one of the following treatments according to a
completely randomized block design:

• COM0: control (basal diet) (no supplementation)

• COM0.25: basal diet plus coconut meal 0.25% of LW/day

• COM0.5: basal diet plus coconut meal 0.5% of LW/day

• COM0.75: basal diet plus coconut meal 0.75% of LW, day

• COM1.0: basal diet plus coconut meal 1.0% of LW, day

Animals and housing

The cattle had an initial weight in the range of 140 to 244 kg and were
allocated to 5 pens so that mean live weights within each pen were similar
(Photo 1). Vaccination was done against epidemic diseases and the cattle
were drenched against internal parasites before the commencement of the
experiment.

Photo 1. The Sindhi cattle housed in
group pens

Photo 2. The coconut meal collected from the
processing factory

Feeding and management

The cattle were adapted gradually to the experimental feeds for two weeks prior to starting the
experiment. The cassava pulp was collected from the Wuson cassava factory in
Binh Phuoc province. Elephant grass was harvested from the cropping areas in
the Center for Research and Technology Transfer, and chopped by machine
prior to offering it to the cattle. Coconut meal was purchased from a
coconut milk factory in Ho Chi Minh city. The feeds were offered two times a
day, at 7.30 am and 3.30 pm. Water was always available.

Data collection and measurements

The cattle were weighed at the beginning and every 14 days, using an
electronic balance. Feeds offered were weighed before giving them to the
cattle. Feed refusals were collected each morning prior to offering fresh
feed and weighed to measure the feed intake. Samples of feeds offered and
refused were collected every 14 days to determine DM and crude protein
according to AOAC (1990) methods. At the end of the experiment, a sample of
mixed eructed and respired gas from each animal was analysed for methane:
carbon dioxide ratio using the Gasmet equipment (GASMET 4030; Gasmet
Technologies Oy, Pulttitie 8A, FI-00880 Helsinki, Finland), based on the
approach suggested by Madsen et al (2008). The cattle were held for 1 hour
in a closed chamber before taking the measurements, so that the gases
emitted from the animal could equilibrate with the air in the environment
(Photo 4). Samples of air in the animal house were also analyzed for the
methane: carbon dioxide ratio.

Photo 3. Electronic scale for weighing the
cattle

Photo 4. Closed chamber used to measure
enteric methane production

Chemical analysis

Samples of feeds offered and residues were analyzed for DM and crude protein (CP) following AOAC (1990) procedures.
Protein solubility was measured by weighing 3 g of sample (DM basis),
followed by shaking in 100 ml of M NaCl for 3 h. The suspension was then
filtered through Whatman No. 4 filter paper and washed 3 times with
distilled water. All the filtrate was then transferred to a kjeldahl flask
for digestion, distillation and titration according to AOAC (1990). Protein
solubility was calculated as the N content of the filtrate as a percentage
of the N in the original sample.

Statistical analysis

Response curves were fitted to the data using linear and quadratic equations
in Microsoft Office Excel software, with level of coconut meal as the
independent variable (X) and the response component (eg: feed intake, weight
gain …..,) as dependent variable (Y).

Results and discussion

Chemical composition of feeds

There were major differences in the solubility of the protein with much lower
values for coconut meal and cassava pulp than for Elephant grass (Table 1).

Table 1.
Composition of dietary ingredients

DM
%

CP in DM
%

Soluble protein,
% of total protein

Cassava pulp

29.4

2.30

28.0

Elephant grass

21.6

12.1

51.8

Coconut meal

92.4

19.8

20.9

Feed intake

DM intake increased with a curvilinear trend as the supplementation with
coconut meal increased, the peak value being reached when coconut meal was
fed at 0.5% of live weight (Table 2; Figure 1). The overall level of dietary
crude protein increased with the level of supplementation of coconut meal
from 8.96% of diet DM with zero coconut meal to 11.7% in diet DM with
coconut meal at 1% of live weight. The overall solubility of the dietary
protein showed the opposite trend declining from 49.8% on the control diet
of elephant grass and cassava pulp to 37.6% at the highest level of coconut
meal supplementation (Table 2).

Growth rate increased with the level of supplementation of coconut meal with
a curvilinear trend (R2 = 0.93) indicating that the optimum level
of supplementation was with coconut meal providing about 50% of the dietary
crude protein. Feed conversion was improved by supplementation with coconut
meal with a linear trend (R2 = 0.88), the high values in general
(28.7 – 20.5) reflecting the low rates of live weight gain (0.205 – 0.329
kg/day). The declining rate of response in live weight gain to increasing
levels of coconut meal supplementation is in accordance with similar studies
in which protein-rich supplements were fed in increasing quantities in diets
rich in carbohydrates (eg: fish meal and molasses-urea, Preston and Leng
1987; cottonseed cake and ammoniated wheat straw, Weixian et al 1994).

Coconut oil meal is rich in oil (18% in DM). At the highest level of coconut
oil meal supplementation the contribution of coconut oil to the diet would
be 4.5%, leading to an overall level of ether-extract in the diet of 5.7%.
This could explain the tendency to lower feed intake at the highest level of
supplementation, as suggested by Beauchemin et al (2007). However,
Phengvilaysouk and Wanapat (2008) reported no effect on feed intake when
coconut oil was added to urea-treated rice straw (equivalent to 7.4% oil in
diet DM) fed to buffaloes.

Table 2.
Mean values for changes in live weight, DM intake, DM conversion and crude protein in diet DM and for cattle

Level of coconut meal, % of LW/day

SEM

p

0

0.25

0.5

0.75

1

Live weight, kg

Initial

194

196.5

204.0

186.0

161.0

15.48

0.375

Final

213.8

220.5

232.5

214.6

193.7

15.03

0.502

Daily gain

0.205

0.247

0.300

0.289

0.329

0.022

0.010

DM intake, kg/d

Coconut meal

0

0.50

1.04

1.44

1.69

Cassava pulp

1.89

1.93

2.02

1.85

1.62

0.023

<0.001

Elephant grass

3.99

4.10

4.27

3.92

3.45

0.083

<0.001

Total

5.88

6.53

7.33

7.21

6.75

DM conversion

28.6

26.4

24.4

24.9

20.5

Crude protein
% in diet DM

8.96

9.80

10.5

11.1

11.7

% soluble*

49.8

45.4

42.1

39.5

37.6

* Protein solubilized by extraction with M NaCl

Figure 1. Proportion of the dietary
intake as elephant grass (EM), cassava pulp (CP) and coconut meal (CLO)
according to the dietary treatments

The ratio of methane to carbon dioxide in eructed gas was reduced with a
curvilinear trend (R2 =0.97) by feeding increasing levels of
coconut meal (Table 3; Figure 5). There are two possible explanations for
the reduction in methane with increasing levels of coconut meal in the diet.
Replacing the elephant grass with coconut meal led to an overall decrease in
the solubility of the dietary protein (from 50 to 40%) and this was directly
related (R 2 = 0.94) to the methane: carbon dioxide ratio
(Figure 6). A similar relationship between methane production and solubility of
the dietary protein was reported by Silivong et al (2016) and was attributed to
the shift in metabolic disposal of hydrogen from methane to acetate when the
balance of fermentative digestion was changed as in the case of feeds escaping
from the rumen to be fermented in the cecum-colon (Leng 2016, personal
communication). The increasing levels of oil from
the coconut meal may also have had a direct effect in reducing rumen methanogenisis
associated with the oil decreasing rumen protozoa as reported in an earlier
paper (Nguyen Thanh Duy et al 2016).

Figure 5. Effect of coconut meal on the ratio of methane to carbon
dioxide in eructed gas from cattle fed elephant grass
and cassava pulp as basal diet

Figure 6.
Relationship between solubility of diet protein and
ratio of methane to carbon dioxide in eructed gas from
cattle fed elephant grass and cassava pulp as basal diet
supplemented with increasing levels of coconut meal

Conclusions

Growth rate was increased, feed conversion was improved and eructed methane
decreased with increasing amounts of coconut oil meal in a basal diet of
elephant grass and cassava pulp.

The solubility of the diet protein was reduced when the coconut meal
concentration in the diet increased and was directly related to the
reduction in eructed methane.

A direct effect of the coconut oil reducing methane production through
indirect effects on the rumen protozoa population may also have contributed
to the reduced methane production.

Acknowledgements

This research was done by the senior author as part of the requirements for
the MSc degree in Animal Production "Specialized in Response to Climate
Change and Depletion of Non-renewable Resources" of Cantho University,
Vietnam. The authors acknowledge support for this research from the MEKARN
II project financed by Sida. They also acknowledge the Research and
Technology Transfer Center, Nong Lam University, Vietnam for providing
infrastructure support.

Silivong P and Preston T R 2015
Effect of water spinach on methane production in an in vitro
incubation with substrates of Bauhiniaacuminata andGuazuma
ulmifolia leaves. Livestock Research for Rural Development. Volume 27,Article #217.Retrieved April 2, 2016, from
http://www.lrrd.org/lrrd27/11/sili27217.htm